There is a need in industry to provide a mechanism which will drive a member in an indexed fashion. Preferably, such mechanism will require relatively low efforts to begin the indexing operation yet will generate high forces to move the member between indexed positions.
In addition to effecting such ends, such a drive mechanism is required to meet the following design criteria. First, after indexing the driven member into position, the drive mechanism must hold the member in its new indexed position until a certain low force is applied against the member. Second, after a certain low force is applied against the member for a certain small distance of the member's travel, a relatively high actuating force is to be applied against the member. This relatively high actuating force is used to drive the member in an indexed fashion through at least one position without requiring any additional externally applied force against the member. Third, after indexing the member into position, the drive mechanism should hold the indexed member in position for a certain time (to prevent overshifting) before the relatively high actuating force applied against the member is lowered. Finally, the drive mechanism should allow multiple indexed movements of the member in quick succession without significant resistance.
Known prior art mechanism are not capable of both meeting industry's need and satisfying all of the above design criteria.